Compression ratio calculator

You need a couple of measurements that are not easy to get in order to calculate your compression ratio, but once you have your figures, here's the calculator. Note that for domed pistons, the volume will be a negative number.

Bore

mm

Stroke

mm

Head volume

cc

Piston volume

cc

Gasket thickness

mm

Cylinder volume

cc

Gasket volume

cc

Compression ratio

:1

For example, a four-cylinder motor with a bore of 79.5 mm, a stroke of 86.4 mm, a head volume of 27 cc, a piston volume of 26 cc, and a 1.75 mm thick head gasket will have a compression ratio of 7.95:1.